The present invention relates to the treatment of contaminated effluent from metal processing operations.
In the metal processing area, many techniques presently being utilized require wet processing. In particular, wet processing is found to be necessary in the manufacture of printed circuit boards, multilayer circuits, flexible circuits, chassis plating, and even the production of memory cores. Associated with the wet processing is the problem of handling the waste water resulting therefrom. This problem has become more severe with stringent local and federal legislation, which regulate the dumping of waste water thereby requiring highly efficient systems for effluent treatment.
The question of how to handle such a problem becomes even more difficult when quantities of water used in such wet processing systems for metal processing run in magnitudes in the area of 100 gallons of water per minute, roughly involving handling approximately 50,000 gallons of water each day. In attempting to solve this problem, many techniques have been devised within the last few years which are directed to the reusing of the water. Most of these techniques in the metal processing area involves re-circulating the water obtained through reverse osmosis techniques, where all the contaminated water is routed through a central stream in which, through evaporation techniques, the contaminants are separated from the main stream and reduced to sludge solids which are easily disposed of. In a few exceptional instances, because of the hazards of some contaminants e.g. chrome or cyanide wastes, specific treatments for reclaiming these specific contaminants are separately effected.
Such systems, in general, have been found to be quite inefficient in the handling of feeding concentrated streams directly to the evaporated stage. The inefficiencies involved include intermediate stages used prior to the evaporator stage for handling sludge due to the heavy concentration of contaminants. In addition, a heavy burden is placed on reverse osmosis membranes and filters, resulting in their frequent replacement and/or cleaning.
In order to overcome the disadvantages of such prior art systems, there is shown a more efficient system for use in metal processing systems which not only provides for more efficient handling of the contaminated water, but in addition, increases the life of reverse osmosis membranes and reduces maintenance efforts on the membranes and replacement of conventional filter units. In providing such advantages, an economic benefit is gained by significantly reducing the costs in running such an improved system. This is attained while still achieving recycling of better than 90 percent of the water being used in the metal processing operation.